Anti-fog composite film and preparation method thereof

Abstract

The invention relates to the technical field of anti-fog films, and particularly discloses an anti-fog composite film and a preparation method thereof.The anti-fog composite film comprises a surface layer printing film, a glue layer and a co-extrusion anti-fog layer which are sequentially stacked from top to bottom; the co-extrusion anti-fog layer comprises a first PA layer, a second adhesive layer, a third PA layer, a fourth adhesive layer, a fifth barrier PE layer, a sixth barrier PE layer and a seventh PE anti-fog layer which are sequentially stacked from top to bottom; the seventh PE anti-fog layer is prepared from 30%-80% of linear low-density polyethylene, 10%-35% of metallocene linear low-density polyethylene, 10%-30% of a polyolefin plastomer, 5%-15% wt of an anti-fog agent and 2%-5% of an anti-blocking agent. The PA layers and the PE layers are arranged in the co-extrusion anti-fogging layer, so that the barrier property of the film is improved, an anti-fogging agent can be effectively and synergistically prevented from migrating to the glue layer, and the problem that a traditional anti-fogging easy-to-uncover film is poor in anti-fogging effect and transparency after being compounded is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-fog films, and particularly relates to an anti-fog composite film and a preparation method thereof. Background Art

[0002] In some food fields such as meat, fruits, fresh foods, and cooked foods, after processing, they are often put into plastic packaging boxes and then sealed with plastic cover films. When the packaged foods are placed in supermarket freezers for sale, due to the change of environmental temperature and the moisture contained in the foods themselves, an opaque water mist is easily generated inside the packaging bags, making it difficult for consumers to carefully observe the appearance quality of the foods inside the packaging, etc., and reducing the attractiveness of purchasing the products. In addition, after the water mist formed on the inner surface of the packaging bag drips into drops, it may drip onto the foods, accelerating the reproduction of bacteria and other microorganisms, resulting in a shortened shelf life of the foods.

[0003] Currently, few plastic films on the market can simultaneously meet the multi-functional requirements of anti-fogging, high transparency, and printability. Traditional anti-fog films are mostly three-layer co-extruded polyethylene films. For the anti-fog composite films prepared by compounding with other biaxially stretched films, since the anti-fogging agent is prone to migrate to the glue layer during the compounding and curing process, the anti-fogging effect of the finished product is not good, and even affects the composite strength.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] In view of the above deficiencies of the prior art, the purpose of the present invention is to provide an anti-fog composite film and a preparation method thereof, aiming to solve the problem that existing plastic films are difficult to simultaneously meet the requirements of anti-fogging and high transparency.

[0006] The technical solution of the present invention is as follows:

[0007] An anti-fog composite film, wherein the anti-fog composite film comprises a surface printing film, a glue layer, and a co-extruded anti-fog layer that are sequentially stacked from top to bottom. The co-extruded anti-fog layer comprises a first PA layer, a second adhesive layer, a third PA layer, a fourth adhesive layer, a fifth barrier PE layer, a sixth barrier PE layer, and a seventh PE anti-fog layer that are sequentially stacked from top to bottom; the seventh PE anti-fog layer is composed of 30%-80% linear low-density polyethylene, 10%-35% metallocene linear low-density polyethylene, 10%-30% polyolefin plastomer, 5%-15% wt of anti-fogging agent, and 2%-5% opening agent.

[0008] The anti-fog composite film, wherein the density of the linear low-density polyethylene is 0.916 - 0.918 g / cm 3, the melt index is 1 - 2 g / 10 min; the grade of the metallocene linear low density polyethylene is Dow Chemical AT6202, and the density is 0.908 g / cm 3 , the melt index is 0.85 g / 10 min; the grade of the polyolefin plastomer is Saudi L1060, and the density is 0.903 g / cm 3 , the melt index is 1.0 g / 10 min; the antiblocking agent is a silica - based antiblocking agent.

[0009] For the anti - fog composite film described above, wherein the total thickness of the co - extruded anti - fog layer is 30 - 200 μm, the first PA layer accounts for 8 - 20% of the total thickness, the second adhesive layer accounts for 8 - 15% of the total thickness, the third PA layer accounts for 8 - 20% of the total thickness, the fourth adhesive layer accounts for 8 - 15% of the total thickness, the fifth PE layer accounts for 10 - 25% of the total thickness, the sixth PE layer accounts for 10 - 25% of the total thickness, and the seventh PE anti - fog layer accounts for 15 - 30% of the total thickness.

[0010] For the anti - fog composite film described above, wherein the first PA layer is composed of 98% wt of PA6 resin, 1% wt of slip agent and 1% wt of processing aid; the third PA layer is composed of 100% wt of PA6 resin; the second adhesive layer and the fourth adhesive layer are both composed of 20% - 35% wt of maleic anhydride - modified polyethylene resin and 65% - 80% wt of linear low density polyethylene; the fifth PE layer and the sixth PE layer are both composed of 40% - 80% wt of linear low density polyethylene, 20% - 60% wt of medium density polyethylene or high density polyethylene.

[0011] For the anti - fog composite film described above, wherein the grade of the PA6 resin is DSM F136E2, and the density is 1.13 g / cm 3 ; the slip agent is one of oleic acid amide, erucic acid amide and silicone - based slip agent; the grade of the maleic anhydride - modified polyethylene resin is Basell PX3060, and the density is 0.924 g / cm 3 ; the density of the linear low density polyethylene is 0.916 - 0.918 g / cm 3 , the melt index is 1 - 2 g / 10 min; the grade of the medium density polyethylene is ExxonMobil 3505mc, and the density is 0.935 g / cm 3 , the melt index is 0.5 g / 10 min; the density of the high density polyethylene is 0.935 - 0.96 g / cm 3 , the melt index is 0.3 - 1.0 g / 10 min.

[0012] For the anti - fog composite film described above, wherein the glue layer is a two - component polyurethane adhesive.

[0013] The anti-fog composite film described above, wherein the surface printed film is one of a biaxially oriented polyamide film, a biaxially oriented polyester film, and a biaxially oriented polypropylene film.

[0014] A method for preparing the anti-fog composite film as described in the present invention, which includes the steps:

[0015] After adding the raw materials of the first PA layer, the second adhesive layer, the third PA layer, the fourth adhesive layer, the fifth barrier PE layer, the sixth barrier PE layer, and the seventh PE anti-fog layer into the corresponding hoppers of each layer and mixing them evenly, they are melted, plasticized, and extruded in the corresponding extruders, blown into a film under the processing conditions of a temperature of 180 - 260 °C, then cooled by the down-blow water cooling method, shaped by a chevron board, drawn and wound, and finally slit and trimmed according to the required width to obtain a co-extruded anti-fog layer;

[0016] Coat a two-component polyurethane adhesive between the surface printed film and the first PA layer and form a glue layer by dry lamination, thereby obtaining the anti-fog composite film.

[0017] Beneficial effects: For the anti-fog composite film provided by the present invention, its first PA layer is laminated with the surface printed film through a polyurethane adhesive, endowing the packaging with rich color patterns, text information, etc.; at the same time, the first PA layer, the third PA layer, the fifth barrier PE layer, and the sixth barrier PE layer are provided in the co-extruded anti-fog layer, increasing the barrier property of the film, and can effectively cooperate to block the migration of the anti-fog agent to the glue layer, solving the problem that the anti-fog effect and transparency are poor after the traditional anti-fog easy-peel film is laminated. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of an anti-fog composite film of the present invention. Detailed Embodiments

[0019] The present invention provides an anti-fog composite film and a method for preparing the same. To make the purpose, technical solution, and effects of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] Due to the strong migration of the anti-fog agent, in traditional composite films, during the lamination and curing processes, the anti-fog masterbatch will strongly migrate to the composite glue layer, resulting in the reduction of the peel strength of the glue layer and the weakening of the anti-fog effect of the anti-fog layer.

[0021] Based on this, the present invention provides an anti-fog composite film, as Figure 1As shown in the figure, the anti-fog composite film includes a surface printing film 10, an adhesive layer 20, and a co-extruded anti-fog layer 30 that are stacked in sequence from top to bottom. The co-extruded anti-fog layer includes a first PA layer 31, a second adhesive layer 32, a third PA layer 33, a fourth adhesive layer 34, a fifth barrier PE layer 35, a sixth barrier PE layer 36, and a seventh PE anti-fog layer 37 that are stacked in sequence from top to bottom. The seventh PE anti-fog layer 37 is composed of 30%-80% linear low-density polyethylene, 10%-35% metallocene linear low-density polyethylene, 10%-30% polyolefin plastomer, 5%-15% anti-fog agent, and 2%-5% opening agent by mass percentage.

[0022] In the present invention, by providing the first PA layer, the third PA layer, the fifth barrier PE layer, and the sixth barrier PE layer in the co-extruded anti-fog layer, these PA layers and PE layers have relatively high density and good barrier properties, which can effectively block the migration of the anti-fog agent to the adhesive layer, so that the anti-fog agent remains in the anti-fog layer to play a better anti-fog function, thus solving the problem of poor anti-fog function after being compounded with the surface printing film.

[0023] In the present invention, the seventh PE anti-fog layer uses both linear low-density polyethylene and metallocene linear low-density polyethylene at the same time. Among them, the density of the linear low-density polyethylene is 0.916-0.918 g / cm 3 , and the melt index is 1-2 g / 10 min; the grade of the metallocene linear low-density polyethylene is Dow Chemical AT6202, and the density is 0.908 g / cm 3 , and the melt index is 0.85 g / 10 min. Linear low-density polyethylene (LLDPE) has a relatively low price, has certain strength, toughness and processing performance, and can provide basic physical properties and economy for the film; metallocene linear low-density polyethylene (mLLDPE) has higher strength, better toughness, puncture resistance and better optical properties, such as transparency and gloss. The combination of the two in the present invention can control the cost through LLDPE while ensuring the film performance, achieving a better balance between performance and cost. LLDPE has relatively good processing performance, requires lower processing equipment, and relatively lower processing temperature and pressure.

[0024] mLLDPE requires higher processing temperature and pressure during the processing process, but has good extrusion performance and blow molding performance. The combination of the two helps to improve the overall processing performance, makes the film production process smoother, and improves production efficiency and product quality.

[0025] The polyolefin plastomer added to the seventh-layer PE anti-fog layer has excellent flexibility and impact resistance, which can improve the softness and impact resistance of the film, making the film less likely to break during use, especially suitable for some application scenarios that require frequent bending or external force impact; it can also reduce the embrittlement temperature of the film, improve the flexibility and toughness of the film in low-temperature environments, broaden the use temperature range of the film, and enable it to maintain good performance in cold regions or low-temperature conditions. As an example, the grade of the polyolefin plastomer is Saudi L1060, and the density is 0.903 g / cm 3 , and the melt index is 1.0 g / 10 min.

[0026] The anti-fog agent added to the seventh-layer PE anti-fog layer is an additive that can effectively prevent the formation of fog on the film surface. It usually contains components such as surfactants, which can reduce the contact angle of water on the film surface, make water vapor form a uniform water film on the film surface instead of condensing into small water droplets, thus avoiding the generation of fog, maintaining the transparency of the film, and improving the visibility and use effect of the film. As an example, the anti-fog agent can be a non-ionic surfactant, such as glycerol monostearate, polyethylene glycol stearate, etc.; the anti-fog agent can also be an ionic surfactant, such as sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, etc.

[0027] The anti-blocking agent added to the seventh-layer PE anti-fog layer is generally some inorganic particles with a certain particle size. During the film production and use process, they can form tiny protrusions on the film surface, increase the surface roughness of the film, reduce the contact area between the films, thereby preventing the films from sticking during winding or storage, facilitating the subsequent processing and use of the films; the anti-blocking agent can also improve the slip performance of the film, making the film easier to be drawn, wound, etc. during the processing process, and also facilitating the unfolding and operation of the film during use. As an example, the anti-blocking agent is a silica-based anti-blocking agent. For example, the grade of the anti-blocking agent is Huayi 1012, and the density is 0.926 g / cm 3 , and the main component of the Huayi 1012 anti-blocking agent is silica, which has good anti-blocking performance, can effectively prevent the films from sticking, and can maintain the transparency and mechanical properties of the film at the same time.

[0028] In some embodiments, the first PA layer is composed of 98% wt of PA6 resin, 1% wt of a slip agent, and 1% wt of a processing aid; the third PA layer is composed of 100% wt of PA6 resin; the second adhesive layer and the fourth adhesive layer are both composed of 20%-35% wt of maleic anhydride-modified polyethylene resin and 65%-80% wt of linear low-density polyethylene; the fifth PE layer and the sixth PE layer are both composed of 40%-80% wt of linear low-density polyethylene and 20%-60% wt of medium-density polyethylene or high-density polyethylene.

[0029] In this embodiment, the combination of the PA layer and the PE layer can effectively prevent the anti-fogging agent from migrating to the glue layer, which is mainly related to their formulation composition and their own properties. The specific mechanism is as follows: The first PA layer is composed of 98% wt of PA6 resin, 1% wt of a slip agent, and 1% wt of a processing aid, and the third PA layer is composed of 100% wt of PA6 resin; PA6 resin is a polyamide material with high crystallinity. The molecular chain of PA6 resin contains polar amide groups, and the intermolecular force is relatively strong, with good compactness and crystallinity. This structure makes the PA layer have a relatively high density, and it is difficult for gas and small-molecule substances to penetrate through; the anti-fogging agent is usually some small-molecule substances with specific chemical structures, and the dense structure of the PA layer can hinder the diffusion of anti-fogging agent molecules, thus playing a barrier role; in addition, there is good adhesion between the PA layer and the adjacent adhesive layer, which can form a stable interface and further prevent the anti-fogging agent from migrating to the glue layer.

[0030] In this embodiment, the fifth PE layer and the sixth PE layer are both composed of 40%-80% wt of linear low-density polyethylene and 20%-60% wt of medium-density polyethylene or high-density polyethylene. Linear low-density polyethylene has a linear molecular structure, and the molecular chains are arranged relatively regularly; medium-density polyethylene or high-density polyethylene has a relatively high density and a relatively high crystallinity. The combination of different-density polyethylenes forms a relatively tight molecular arrangement structure. Linear low-density polyethylene provides certain flexibility and processing performance, while medium-density polyethylene or high-density polyethylene increases the density and crystallinity of the material. This combination makes the PE layer have good barrier properties and can block the penetration of anti-fogging agent molecules. At the same time, the compatibility between the PE layer and the adjacent PA layer and the adhesive layer is good, which can form a stable interlayer structure and reduce the possibility of the anti-fogging agent migrating to the glue layer through the interlayer gap.

[0031] In this embodiment, the PA layer and the PE layer have a synergistic barrier effect. The PA layer and the PE layer are arranged in multiple layers to form a multi-layer barrier structure. The high crystallinity and polar characteristics of the PA layer complement the close molecular arrangement structure of the PE layer, further improving the overall barrier performance. During the migration process of the anti-fog agent molecules, they need to pass through the PA layer and the PE layer in sequence, increasing the tortuosity of the migration path, thereby effectively preventing the migration of the anti-fog agent to the glue layer. The interfacial interactions between the PA layer and the PE layer and between them and the adhesive layer also have an important impact on the barrier performance. Due to the good adhesion between the PA layer and the PE layer and the adhesive layer, the intermolecular forces at the interface are relatively strong, forming a stable interfacial structure. This interfacial structure can prevent the diffusion of anti-fog agent molecules between the layers, making it more difficult for the anti-fog agent to break through the multi-layer structure and migrate to the glue layer.

[0032] In some embodiments, the grade of the PA6 resin is DSM F136E2, and the density is 1.13 g / cm 3 ; the slip agent is one of oleic acid amide, erucic acid amide and silicone slip agents; the grade of the maleic anhydride-modified polyethylene resin is Basell PX3060, and the density is 0.924 g / cm 3 ; the density of the linear low-density polyethylene is 0.916 - 0.918 g / cm 3 , and the melt index is 1 - 2 g / 10 min; the grade of the medium-density polyethylene is ExxonMobil 3505mc, and the density is 0.935 g / cm 3 , and the melt index is 0.5 g / 10 min; the density of the high-density polyethylene is 0.935 - 0.96 g / cm 3 , and the melt index is 0.3 - 1.0 g / 10 min, but not limited thereto.

[0033] In some embodiments, the total thickness of the co-extruded anti-fog layer is 30 - 200 μm. The first PA layer accounts for 8 - 20% of the total thickness, the second adhesive layer accounts for 8 - 15% of the total thickness, the third PA layer accounts for 8 - 20% of the total thickness, the fourth bonding layer accounts for 8 - 15% of the total thickness, the fifth PE layer accounts for 10 - 25% of the total thickness, the sixth PE layer accounts for 10 - 25% of the total thickness, and the seventh PE anti-fog layer accounts for 15 - 30% of the total thickness.

[0034] In this embodiment, the first PA layer and the third PA layer each account for 8-20% of the total thickness. The PA layer has a high crystallinity and a dense molecular structure, and has good barrier properties against gases, water vapor, anti-fog agent molecules, etc. An appropriate thickness can ensure that it forms an effective barrier in the co-extruded anti-fog layer, preventing external water vapor from entering and the internal anti-fog agent from migrating to other layers, thereby prolonging the anti-fog life of the film and maintaining its barrier properties. The fifth PE layer and the sixth PE layer each account for 10-25% of the total thickness. The PE layer formed by combining polyethylene with different densities also has good barrier properties. Cooperating with the PA layer, it further enhances the barrier effect of the entire co-extruded anti-fog layer on substances such as water vapor and oxygen, and improves the comprehensive performance of the film. The second adhesive layer and the fourth bonding layer each account for 8-15% of the total thickness. This thickness can ensure that the adhesive layer plays a good bonding role between the PA layer and the PE layer, making each layer closely combined to form a stable composite structure, preventing interlayer separation, and ensuring the integrity and reliability of the film during use. The seventh PE anti-fog layer accounts for 15-30% of the total thickness. This layer contains functional components such as anti-fog agents. An appropriate thickness can ensure an adequate content of anti-fog agents, enabling it to form a uniform anti-fog coating on the film surface, effectively reducing the surface tension of water, and causing water vapor to form a uniform water film on the film surface, thereby achieving a good and lasting anti-fog effect. In this embodiment, through the reasonable setting of the thickness of each layer, within the range of the total thickness of the co-extruded anti-fog layer being 30-200 um, the performance of each layer can be fully exerted and cooperate with each other, achieving a better balance in terms of barrier performance, bonding performance, anti-fog performance, etc., meeting the requirements of different application scenarios for the film performance, and at the same time being beneficial to controlling production costs and the feasibility of the production process. For example, when packaging food, it can effectively prevent water vapor and oxygen from entering the package interior, maintaining the freshness of the food, and at the same time the anti-fog function enables consumers to clearly see the food inside the package.

[0035] In some embodiments, the glue layer is a two-component polyurethane adhesive, and the two-component polyurethane adhesive is coated between the surface printed film and the first PA layer by dry lamination. In this embodiment, dry lamination refers to a process in which the solvent is volatilized by heating and drying, and then the surface printed film and the first PA layer are laminated together under a certain pressure. In this embodiment, the surface printed film is one of a biaxially oriented polyamide film, a biaxially oriented polyester film, and a biaxially oriented polypropylene film, that is, graphic information is transferred to the surface film by printing, making the package have rich color patterns and product-related text information.

[0036] In some embodiments, a method for preparing an anti-fog composite film is further provided, which is characterized by including the steps of: adding the raw materials of the first PA layer, the second adhesive layer, the third PA layer, the fourth adhesive layer, the fifth barrier PE layer, the sixth barrier PE layer, and the seventh PE anti-fog layer into the corresponding hoppers of each layer respectively, mixing them evenly, melting, plasticizing, and extruding them in the corresponding extruders, blowing the film under the processing conditions of a temperature of 180 - 260 °C, then cooling it by the down-blow water cooling method, shaping it with a chevron plate, drawing and winding it up, and finally slitting and trimming the edges according to the required width to obtain a co-extruded anti-fog layer; coating a two-component polyurethane adhesive between the surface printed film and the first PA layer and forming a glue layer by the dry lamination method, thereby obtaining the anti-fog composite film.

[0037] In this embodiment, the corresponding extruders are used to melt, plasticize, and extrude the raw materials of each layer, and the processing parameters such as temperature, pressure, etc. can be precisely controlled according to the characteristics of different raw materials, so that the raw materials of each layer are formed under the best conditions, improving the production efficiency and product quality. The multi-layer simultaneous extrusion method can also achieve continuous production, reducing the production processes and time. Blowing the film under the processing conditions of 180 - 260 °C, this temperature range is suitable for the processing of various polymer raw materials, which helps the films of each layer to achieve good physical properties such as strength, toughness, and barrier properties, etc. At the same time, the down-blow water cooling method can quickly cool and shape the film, which helps to improve the crystallinity and orientation degree of the film, further improving the film properties such as transparency and mechanical strength, etc. The chevron plate shaping can precisely control the shape and size of the blown film, ensuring the thickness uniformity and stability of the film, improving the appearance quality and dimensional accuracy of the film, and being beneficial to subsequent processes such as drawing and winding and slitting. Coating a two-component polyurethane adhesive between the surface printed film and the first PA layer and forming a glue layer by the dry lamination method, the two-component polyurethane adhesive has good bonding performance and can form a firm bond between the two layers. The dry lamination process can precisely control the coating amount and drying degree of the glue, ensuring the lamination quality, making the anti-fog composite film have good interlayer bonding force and not being prone to delamination.

[0038] The present invention will be further explained and illustrated through specific embodiments as follows:

[0039] Example 1

[0040] An anti-fog composite film, the anti-fog composite film includes a surface printed film, a glue layer, and a co-extruded anti-fog layer that are stacked in sequence from top to bottom. The total thickness of the co-extruded anti-fog layer is 110 um, and the co-extruded anti-fog layer includes a first PA layer, a second adhesive layer, a third PA layer, a fourth adhesive layer, a fifth barrier PE layer, a sixth barrier PE layer, and a seventh PE anti-fog layer that are stacked in sequence from top to bottom.

[0041] The first PA layer accounts for 13% of the total thickness, the second adhesive layer accounts for 10% of the total thickness, the third PA layer accounts for 13% of the total thickness, the fourth adhesive layer accounts for 10% of the total thickness, the fifth PE layer accounts for 12% of the total thickness, the sixth PE layer accounts for 12% of the total thickness, and the seventh PE anti-fog layer accounts for 30% of the total thickness.

[0042] The first PA layer is composed of 98% wt of PA6 resin, 1% wt of slip agent, and 1% wt of processing aid. The third PA layer is composed of 100% wt of PA6 resin. The second adhesive layer and the fourth adhesive layer are composed of 25% wt of maleic anhydride modified polyethylene resin and 75% wt of linear low density polyethylene. The fifth PE layer is composed of 70% wt of linear low density polyethylene and 30% wt of high density polyethylene. The sixth PE layer is composed of 40% wt of medium density polyethylene and 60% of linear low density polyethylene. The seventh PE anti-fog layer is composed of 45% linear low density polyethylene, 20% metallocene linear low density polyethylene, 20% of polyolefin plastomer, 12% wt of anti-fog masterbatch, and 3% opening agent.

[0043] The PA6 resin of the first PA layer and the second PA layer has the brand name of DSM F136E2 and a density of 1.13 g / cm 3 The maleic anhydride modified polyethylene resin of the second adhesive layer and the fourth adhesive layer has the brand name of Basell PX3060 and a density of 0.924 g / cm 3 The high density polyethylene of the fifth PE layer has a density of 0.95 g / cm 3 and a melt index of 0.8 g / 10 min; The medium density polyethylene of the sixth PE layer has the brand name of ExxonMobil 3505mc and a density of 0.935 g / cm 3 and a melt index of 0.5 g / 10 min. The linear low density polyethylene of the fifth PE layer and the sixth PE layer has the brand name of Basell 2420H and a density of 0.924 g / cm 3 and a melt index of 1.9 g / 10 min; The opening agent of the seventh PE anti-fog layer has the brand name of Huayi 1012 and a density of 0.926 g / cm 3 The polyolefin plastomer of the seventh PE anti-fog layer has the brand name of Saudi S1060L and a density of 0.903 g / cm 3 and a melt index of 1.0 g / 10 min. The metallocene linear low density polyethylene of the seventh PE anti-fog layer has the brand name of Dow AT6202 and a density of 0.908 g / cm 3, the melt index is 0.85 g / 10 min, and the linear low-density polyethylene of the seventh-layer PE anti-fog layer has the trade name ExxonMobil 1002AY and a density of 0.918 g / cm 3 , and the melt index is 2 g / 10 min.

[0044] The preparation method of the above anti-fog composite film is as follows: The first-layer PA layer, the second-layer adhesive layer, the third-layer PA layer, the fourth-layer adhesive layer, the fifth-layer PE layer, the sixth-layer PE layer, and the seventh-layer PE anti-fog layer are respectively added to the corresponding hoppers according to the above raw material ratios, mixed evenly, melted, plasticized, and extruded in the corresponding extruders, and blown into a film under the processing conditions of a temperature of 180-260 °C, then cooled by the downward blowing water cooling method, shaped by the chevron plate, and drawn and wound; finally, according to the required width, the single-piece film is obtained by slitting and trimming the edges;

[0045] A surface layer is further laminated on the first-layer PA layer. The surface layer is a biaxially oriented polyester film with a thickness of 12 μm, and graphic information can be transferred to the surface layer film by printing;

[0046] An adhesive layer is provided between the surface layer and the first-layer PA layer; the adhesive layer is a two-component polyurethane adhesive, and the two-component polyurethane adhesive is coated on the surface layer film by dry lamination.

[0047] Example 2

[0048] The difference between this example and Example 1 is that: the seventh PE layer is composed of 49% linear low-density polyethylene, 20% metallocene linear low-density polyethylene, 20% polyolefin plastomer, 8% wt anti-fog masterbatch, and 3% opening agent.

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 1 is that: the seventh PE layer is composed of 53% linear low-density polyethylene, 20% metallocene linear low-density polyethylene, 20% polyolefin plastomer, 4% wt anti-fog masterbatch, and 3% opening agent.

[0051] Comparative Example 2

[0052] The difference between this example and Example 1 is that: the seventh PE layer is composed of 47% linear low-density polyethylene, 25% metallocene linear low-density polyethylene, 25% polyolefin plastomer, and 3% opening agent.

[0053] Referring to the detection method of GBT31726-2015, the anti-fog performance of the anti-fog films prepared in Examples 1-2 and Comparative Examples 1-2 was tested, and the anti-fog effects at 4 hours, 24 hours, and 3 days were tested.

[0054] The evaluation criteria are shown in Table 1 as follows:

[0055] Table 1 Evaluation Criteria

[0056]

[0057] According to the test standard GB / T1040.3-2006, a tensile tester is used to test the tensile strength.

[0058] According to the test standard GB / T1038-2008, a haze meter is used to test the haze and light transmittance of the anti-fog film.

[0059] The test results are shown in Table 2 as follows:

[0060] Table 2 Test Results

[0061]

[0062] It can be seen from the results in Table 2 that in terms of anti-fog performance, considering Examples 1-2 and Comparative Examples 1-2, the anti-fog effect begins to deteriorate as the dosage of the anti-fog masterbatch decreases. When the concentration is as low as a certain level (below 5%), the anti-fog effect is not good. Maintaining a moderate concentration of 5%-15%wt can not only maintain a good anti-fog effect but also have good transparency.

[0063] In terms of transparency, considering Examples 1-2 and Comparative Examples 1-2, the transparency can reach a good state.

[0064] Generally speaking, due to the strong migration of the anti-fog agent, in traditional composite films, during the compounding and curing processes, the anti-fog masterbatch will strongly migrate to the composite glue layer, resulting in a decrease in the peel strength of the glue layer and a weakening of the anti-fog effect of the anti-fog layer. In the seven-layer co-extruded anti-fog film, the PA layer and the PE layer have a synergistic barrier effect. The combination of the two has a high density and good barrier properties, which can effectively block the migration of the anti-fog agent to the glue, solve the problem of poor anti-fog function after being compounded with the surface printing film, and thus enable the anti-fog agent to remain in the anti-fog layer to play a better anti-fog function.

[0065] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description. All such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. An anti-fog composite film, characterized in that: The anti-fog composite film comprises a surface printed film, a glue layer and a co-extruded anti-fog layer which are sequentially stacked from top to bottom; the co-extruded anti-fog layer comprises a first PA layer, a second adhesive layer, a third PA layer, a fourth adhesive layer, a fifth barrier PE layer, a sixth barrier PE layer and a seventh PE anti-fog layer which are sequentially stacked from top to bottom; the seventh PE anti-fog layer consists of 30%-80% of linear low-density polyethylene, 10%-35% of metallocene linear low-density polyethylene, 10%-30% of polyolefin plastomer, 5%-15% of anti-fog agent and 2%-5% of anti-blocking agent by mass percentage.

2. The anti-fog composite film according to claim 1, characterized in that: The density of the linear low-density polyethylene is 0.916-0.918 g / cm 3 , melt index is 1-2g / 10min; the grade of the metallocene linear low-density polyethylene is Dow Chemical AT6202, and the density is 0.908g / cm 3 The melt index is 0.85 g / 10 min; the grade of the polyolefin plastomer is Saudi L1060, and the density is 0.903 g / cm 3 , the melt index is 1.0g / 10min; the opening agent is a silicon dioxide opening agent.

3. The anti-fog composite film according to claim 1, characterized in that: The total thickness of the co-extruded anti-fog layer is 30-200um, the first PA layer accounts for 8-20% of the total thickness, the second adhesive layer accounts for 8-15% of the total thickness, the third PA layer accounts for 8-20% of the total thickness, the fourth adhesive layer accounts for 8-15% of the total thickness, the fifth PE layer accounts for 10-25% of the total thickness, the sixth PE layer accounts for 10-25% of the total thickness, and the seventh PE anti-fog layer accounts for 15-30% of the total thickness.

4. The anti-fog composite film according to claim 1, characterized in that: The first PA layer is composed of 98%wt PA6 resin, 1%wt lubricant and 1%wt processing aid; the third PA layer is composed of 100%wt PA6 resin; the second adhesive layer and the fourth adhesive layer are both composed of 20%-35%wt maleic anhydride modified polyethylene resin and 65%-80%wt linear low-density polyethylene; the fifth PE layer and the sixth PE layer are both composed of 40%-80%wt linear low-density polyethylene and 20%-60%wt medium-density polyethylene or high-density polyethylene.

5. The anti-fog composite film according to claim 4, characterized in that: The PA6 resin is DSM F136E2 with a density of 1.13 g / cm 3 The lubricant is one of oleamide, erucic acid amide and silicone lubricant; the brand of maleic anhydride modified polyethylene resin is Basel PX3060, with a density of 0.924g / cm 3 The density of the linear low-density polyethylene is 0.916-0.918 g / cm 3 , the melt index is 1-2g / 10min; the grade of the medium density polyethylene is ExxonMobil 3505mc, and the density is 0.935g / cm 3 , the melt index is 0.5g / 10min; the density of the high-density polyethylene is 0.935-0.96g / cm 3 , the melt index is 0.3-1.0g / 10min.

6. The anti-fog composite film according to claim 1, characterized in that: The glue layer is a two-component polyurethane adhesive.

7. The anti-fog composite film according to claim 1, characterized in that: The surface printing film is one of a biaxially stretched polyamide film, a biaxially stretched polyester film and a biaxially stretched polypropylene film.

8. A method for preparing the anti-fog composite film according to any one of claims 1 to 7, characterized in that: Includes steps: The raw materials of the first PA layer, the second adhesive layer, the third PA layer, the fourth adhesive layer, the fifth barrier PE layer, the sixth barrier PE layer and the seventh PE anti-fog layer are added to the corresponding hoppers of each layer and mixed evenly, then melted, plasticized and extruded in the corresponding extruder, blown under the processing condition of 180-260°C, cooled by downward water cooling, shaped by a herringbone splint, pulled and rolled, and finally cut the flash according to the required width to obtain the co-extruded anti-fog layer; A two-component polyurethane adhesive is coated between the surface printed film and the first PA layer and a glue layer is formed by dry lamination to obtain the anti-fog composite film.

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